Generally, a hydraulic excavator as a typical example of construction machines is constituted by an automotive lower traveling structure, an upper revolving structure which is swingably mounted on the lower traveling structure, and a working mechanism liftably mounted on the front side of the upper revolving structure.
The upper revolving structure is largely constituted by a revolving frame forming a supporting structure, a cab which is provided on the front side of the revolving frame and where an operator gets on board, an engine mounted on the rear side of the revolving frame, a hydraulic pump mounted on one longitudinal side of the engine, and an exhaust gas treatment device connected to an exhaust manifold of the engine through an exhaust pipe.
As such exhaust gas treatment devices, exhaust gas purifying devices for removing harmful substances in exhaust gas, muffler devices for reducing the noise of the exhaust gas, and the like are known. In this case, the exhaust gas purifying devices include a particulate matter removing device for trapping and removing particulate matter (PM), a NOx purifying device for purifying nitrogen oxides (NOx), and the like, and these may be used in combination.
Here, a support member is mounted on the engine in such a manner as to protrude over the upper side of the hydraulic pump, and the exhaust gas treatment device is arranged to be mounted to the support member. At this time, as the exhaust gas treatment device is mounted to the engine through the support member, the exhaust gas treatment device constitutes the same vibration system as that of the engine, so that the exhaust gas treatment device can be fixedly mounted on the support member (see, for example, Patent Literatures 1 and 2).    Patent Literature 1: Japanese Patent Laid-Open No. 2003-120277 A    Patent Literature 2: Japanese Patent Laid-Open No. 2004-293495 A
Incidentally, with the hydraulic excavator in accordance with the above-described Patent Literature 1, the exhaust gas treatment device is arranged to be fixed on the support member mounted on the engine. In this case, since the engine and the exhaust gas treatment device constitute the same vibration system, the exhaust gas treatment device can be fixedly mounted on the support member by using bolts and the like.
However, since high-frequency vibrations of the engine are directly transmitted to the exhaust gas treatment device, there is a problem in that exhaust gas treatment members and the like constituting the exhaust gas treatment device can be damaged by these vibrations.